The invention relates to an apparatus for injection system for an internal-combustion engine which has a plurality of separate inlet ports for each cylinder of the engine. An intake pipe for each cylinder encompasses these inlet ports, and a downstream injection nozzle injects fuel into the intake pipe.
In German Published Unexamined Patent Application (DOS) No. 2,414,022, a fuel supply system for an applied-ignition internal-combustion engine is shown which has two gas inlet valves per cylinder. Single intake pipes, each having a fuel valve, lead from the intake pipe of the internal-combustion engine, to the gas inlet valves. In this arrangement, each cylinder has a first gas inlet valve assigned to the main combustion chamber and a second gas inlet valve assigned to a secondary combustion chamber. The two combustion chambers are connected by a flame port. Inside the secondary chamber is a spark plug, by which the constantly rich fuel/air mixture is ignited. The flame front directed through the flame port from the secondary combustion chamber to the main combustion chamber is used to ignite the fuel/air mixture there. The fuel/air mixture is adapted to the changing operating conditions of the internal-combustion engine.
A disadvantage of the above arrangement is that in the upper engine load and lower speed ranges, the fuel/air mixture is not mixed thoroughly enough. This is due to the low velocity of the intake air flow and the remote positioning of the fuel valve from the gas exchange valve. The poor fuel/air mixing causes speed variations and unsatisfactory emissions.
An injection system is described in the German language periodical "technik mot" 11/1984 titled "Kopfarbeit", in which two separate inlet ports are provided for each cylinder. The two inlet ports are combined in a single intake pipe for each cylinder. A web wall in the region of the cylinder head in the single intake pipe subdivides the single intake pipe into two separate intake pipe sections. An injection nozzle is located upstream of the web wall in the single intake pipe. The internal-combustion engine with this injection system does not exhibit satisfactory response behavior in non-steady-state operation and subsequent exhaust treatment is hampered.
In British Patent Specification No. 1,351,771, an intake system for an internal-combustion engine is shown which includes a manifold intake pipe from which single intake pipes lead to the inlet valves of the cylinder. Fuel injection nozzles are located upstream of the gas exchanging valves in the single intake pipes. Inside the manifold intake pipe is a multi-hole fuel nozzle for supplying fuel during idling.
The disadvantages of the above system are the poor response behavior of the internal-combustion engine to load cycles, and poor running in the lower speed range. These are attributable to the remote arrangement of the multi-hole fuel nozzle from the gas exchange valve in the manifold intake pipe. During idling, the air speed in the manifold intake pipe is too low to generate adequate turbulences for mixing the fuel/air mixture in the combustion chamber.
An object of the invention is to ensure a constant, thorough mixing of the fuel/air mixture in the intake pipe even at the lower load and upper speed ranges of the internal-combustion engine.
This and other objects are attained by the present invention by providing in an intake pipe of an injection system a subdividing means in the region of the cylinder head for subdividing the intake pipe into separate intake pipe sections. The subdividing means has a mixing chamber into which fuel is injected by at least one injection nozzle. The subdividing means also has shot channels for communicating fuel from mixing chamber to each of the separate intake pipe sections.
An advantageous feature of preferred embodiments of the present invention is an idle air port in the subdividing means which supplies air to the mixing chamber. In the air port, the intake air reaches a high speed, such that a good, thorough mixing of the fuel/air mixture in the cylinder is ensured and the emission during idling is reduced. Due to the intense flow of intake air around the fuel injection nozzle, no fuel residues are left behind on the fuel injection nozzle or in the mixing chamber. The fuel/air mixture for idling operation is therefore homogenous. This stabilizes the idling speed, allowing it to be adjusted to a low speed.
A feature of preferred embodiments of the present invention is the second fuel injection nozzle which is upstream of the subdividing means This nozzle can be switched on when the engine is operating at full load, to inject more fuel to the cylinder when it is needed.